Relaxation dynamics of metallic systems in the liquid/glass transition region

Peer ReviewedPostprint (published version

Study on Mechanical Relaxations of 7075 (Al–Zn–Mg) and 2024 (Al–Cu–Mg) Alloys by Application of the Time-Temperature Superposition Principle

The viscoelastic response of commercial Al–Zn–Mg and Al–Cu–Mg alloys was measured with a dynamic-mechanical analyzer (DMA) as a function of the temperature (from 30 to 425ºC) and the loading frequency (from 0.01 to 150 Hz). The time-temperature superposition (TTS) principle has proven to be useful in studying mechanical relaxations and obtaining master curves for amorphous materials. In this work, the TTS principle is applied to the measured viscoelastic data (i.e., the storage and loss moduli) to obtain the corresponding master curves, and to analyze the mechanical relaxations responsible for the viscoelastic behavior of the studied alloys. For the storage modulus it was possible to identify a master curve for a low-temperature region (from room temperature to 150ºC) and, for the storage and loss moduli, another master curve for a high-temperature region (from 320 to 375ºC). These temperature regions are coincidental with the stable intervals where no phase transformations occur. The different temperature dependencies of the shift factors for the identified master curves, manifested by different values of the activation energy in the Arrhenius expressions for the shift factor, are due to the occurrence of microstructural changes and variations in the relaxation mechanisms between the mentioned temperature regions.Peer ReviewedPostprint (published version

Heterogeneous distribution in ATLAS

The ATLAS platform allows unsophisticated programmers to include advanced features in their applications with no or very little extra information and effort. These features include network distribution of cooperating processes, a powerful macro-language, a flexible journaling system and some other mechanisms directly related to graphics applications problems. In this report we describe how ATLAS is able to distribute the application processes among different architectures without needing a previous configuration information of the available processes for each architecture.Postprint (published version

Murillo in the spanish enlightenment literature

Este artículo analiza la literatura española de la Ilustración sobre Murillo. El pintor sevillano había aparecido en diversas publicaciones españolas anteriores a mediados del siglo XVIII. No era un desconocido, pero durante la Ilustración se realizaron contribuciones muy destacadas y en renovadas direcciones, tanto sobre su trayectoria y su obra, como sobre su significado cultural y su proyección pública.This paper focuses on Murillo’s Spanish Enlightenment Literature. Murillo had appeared in various publications prior to the middle of the 18th century. However, during the Enlightenment, very important contributions were made, about his career and his work, as well as about its cultural meaning and its public influence

3D numerical study of the transient behaviour on plasticity induced crack closure

Daniel Camas, Fernando Antunes, Pablo Lopez-Crespo, Antonio Gonzalez-Herrera, 3D Numerical Study of the Transient Behaviour on Plasticity Induced Crack Closure, Abstract Booklet of the MSMF9, Edited by Pavel Sandera, Brno University of Technology, 2019, pp. 136.The numerical analysis of the plasticity induced crack closure requires the development of the plastic wake. Transient behaviour is observed when the crack starts to grow. The plastic wake length has an influence on the crack closure results and a great impact on the computational cost. Previous works have analysed the influence of this parameter considering bi-dimensional specimens in either plane strain or plane stress conditions. Lately, some three-dimensional models have appeared in order to analyse the crack closure phenomenon. The main scope of this study is to quantify and comprehend the minimum length required to stabilise the crack opening and closure values considering a three-dimensional model. On this purpose, a CT aluminium specimen has been modelled three-dimensionally and several calculations have been made in order to evaluate the influence of the simulated plastic wake. The numerical analysis is made in terms of crack closure and opening values.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

A numerical analysis of the plastic wake influence on plasticity induced crack closure

Fatigue crack closure has been studied by means of finite element method since long time ago. Most work has been performed considering bi-dimensional models. Lately, the use of threedimensional models has been extended. Nevertheless, the methodology employed has been taken from that developed for bi-dimensional cases. There are a great number of previous bi-dimensional studies which analyse different numerical parameters and optimise them. The current computational capabilities allow a comprehensive study of the influence of the different modelling parameters in a similar way to those studies carried out with bidimensional models, with the advantage, that the evolution along the thickness of the analysed parameters can be taken into consideration. In particular, one of the key issues is related to the plastic wake length which is developed during the previous loading cycles. This residual stresses have a great influence on the crack opening and closure values. As the numerical analysis are complex and computationally expensive, the length of the simulated wake is a critical parameter. In this work, a comprehensive study of the effect of the plastic wake in fatigue crack closure is made. On this purpose, a CT aluminium specimen has been modelled three-dimensionally and several calculations have been made in order to evaluate the influence of the simulated plastic wake length. The numerical analysis is made in terms of crack closure and opening values as in terms of the stress and strain fields near the crack front.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Trazos de una naciente historia del arte : los dibujos de la lonja de Palma para la Memoria de Jovellanos

Las Memorias sobre las fábricas góticas de Mallorca que Jovellanos escribió (1806-1808) como prisionero de Bellver han sido reconocidas no sólo como una aportación clave al conocimiento de la arquitectura gótica de la isla, sino también como una contribución de primer orden a la naciente historia del arte en España. Aunque publicadas repetidamente, se daban por perdidos los dibujos que se sabe las complementaban. La localización de una nueva versión manuscrita, ésta sí con las láminas, nos ha impulsado a releer la Memoria sobre la lonja -la más lograda de cuantas escribiera el ilustrado-, a dar a conocer las cinco láminas que la acompañan y a plantearnos la importancia que los dibujos tuvieron para que Jovellanos pudiera llevar a cabo las Descripciones de los monumentos y para que Ceán Bermúdez, el destinatario de los textos, conociera mejor las obras tratadas por la pluma del ilustre gijonés.The Memorias of the Gothic buildings that Jovellanos wrote (1806-1808) as a prisoner in the castle of Bellver (1802-1808) have been recognized not only as an essential element for interpreting the Gothic architecture of the island of Mallorca, but also as a major contribution to the developing art-historical discipline in Spain. Despite the fact that the Memorias had been repeatedly published, the drawings originally accompanying them were assumed to be lost. However, the recent fi nding of a new manuscript version of the text, now complemented by its illustrations, has prompted us to present these fi ve drawings as well as revisit the Memoria of the Lonja, the best of all the Memorias that Jovellanos wrote. This fi nding has also lead us to refl ect upon the importance the plates had for Jovellanos to be able to carry out his Descripciones of the monuments, as well as for Ceán Bermudez -the actual recipient of Jovellanos' texts- to have a better understanding of the monuments so skillfully «described» by the illustrious son of Gijón